Step 1: Getting Started With Blender
Left Mouse Button (LMB) is generally in charge of moving stuff around
Middle Mouse Button (MMB) is what changes the viewpoint
Right Mouse Button (RMB) is what selects and deselects
A is select all / deselect all
E is Extrude
S is Scale
Space brings up a menu for item creation
So just press A until all of the items are pink then press Del then
Step 2: Make a Plane
Step 3: Subdivide
First enter Edit Mode
Then click Subdivide
The plane should now look like the picture.
If this doesn't work, make sure you have selected the plane by pressing A
Step 4: Give It the Shuriken Shape
To select a corner, make sure everything is deselected (selected points, or vertices, turn yellow)
RMB on the corner then drag it out and use LMB to set the vertex there.
Do this to all four sides.
Step 5: Change the Viewpoint
First, bring your mouse up near the top where it should turn into a double-arrow re-sizing cursor.
Next Right Click and select Split Area.
Click somewhere in the middle of the screen to complete the vertical split.
Do this again on the right side to give us a third window.
Now press Num 1 while your mouse is over the left window,
Num 7" while your mouse is over the top window,
and Num 3 while your mouse is over the bottom window.
Step 6: Extrude the Shuriken Upwards
Select all by pressing A
Extrude upwards by pressing E
Continue up until it is about half as thick as you want the finished product to be then press LMB
Step 7: Give the Shuriken a Nice, Pointy Edge
Press S To start scaling.
Move the mouse until the shuriken looks something like the one in the picture.
Step 8: Mirroring the Shuriken
Use A to select all of the vertices
On the bottom right of the screen there should be a button called "Add Modifier".
Click on that then select "Mirror".
Make sure that the settings match the picture.